1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus, and more particularly, to a cooling apparatus for lowering a temperature of a body that is increased by heat generated from a fusing apparatus.
2. Description of the Related Art
A electrophotographic apparatus generally forms a latent electrostatic image on a photosensitive medium, such as a photosensitive belt or a photosensitive drum, develops the latent electrostatic image with toner, and transfers the developed latent electrostatic image to a sheet of paper to form an image.
The electrophotographic apparatus is classified into one of wet and dry electrophotographic printers according to a kind of toner. The dry electrophotographic printer uses powdered toner while the wet electrophotographic printer uses a liquid developer containing volatile liquid carrier toner. The wet electrophotographic printer can perform quality printing, compared to the dry electrophotographic printer, and prevent damage occurring due to harmful toner dust.
FIG. 1 is a cross-sectional view of a conventional dry electrophotographic image forming apparatus 100. FIG. 2 is a perspective view explaining an airflow generated by a cooling apparatus 170 shown in FIG. 1.
Referring to FIG. 1, the dry electrophotographic image forming apparatus 100 includes a developer unit 120, a transfer unit 130, a fusing unit 140, a paper supplying unit 160, and the cooling apparatus 170.
The developer unit 120 coats a latent electrostatic image formed on a photosensitive drum 121 by a laser scanning unit 110 with a developer supplied from a developer tank 122 to form a toner image.
The transfer unit 130 is installed so as to be disposed opposite to the photosensitive drum 121 to rotate together with the photosensitive drum 121. A sheet of paper P is inserted between the photosensitive drum 121 and the transfer unit 130 and simultaneously, the toner image formed on the photosensitive drum 121 is transferred to the paper.
The fusing unit 140 is installed in a paper discharging pathway and fuses the toner image which has been transferred to the paper by the transfer unit 130 to the paper by predetermined heat and pressure.
The paper supplying unit 160 supplies the paper P, to which the toner image will be transferred, to a transfer nip between the photosensitive drum 121, on which the toner image has been formed, and the transfer unit 130. The paper supplying unit 160 includes a pickup roller 161 and transfer rollers 162 and 163. The pickup roller 161 picks up the paper P stacked on a tray 152 supported by a spring 153 in a cassette 151 that is installed to be detached from and attached to a printer body, and supplies the picked-up paper P into a printer body. The transfer rollers 162 and 163 transfer the paper P which has been picked up by the pickup roller 161 inside the printer body.
The cooling apparatus 170 maintains a temperature in the dry electrophotographic image forming apparatus 100 to a predetermined temperature by lowering the temperature increased by heat that is generated in the fusing unit 140 and is spread around. The cooling apparatus 170 is installed on a front frame 181 (See FIG. 2) to be disposed between the fusing unit 140 and the developer unit 120 and includes a first opening 172 and a cooling fan 171. The first opening 172 is formed in a back frame 182 (See FIG. 2). The cooling fan 171 allows external air having a low temperature to flow into the printer body through a second opening 173 which is formed in a side frame 183 that is installed to be perpendicular to the front and back frames 181 and 182.
When the cooling fan 171 operates, a pressure difference occurs in the printer body of the dry electrophotographic image forming apparatus 100. Due to the pressure difference, when the external air having the low temperature flows into the printer body through the first and second openings 172 and 173, internal air whose temperature is increased by heat generated from the fusing unit 140 is discharged outside. As a result, the temperature in the printer body drops so as to be maintained at the predetermined temperature.
Referring to FIG. 2, the external air induced through the first and second openings 172 and 173 by an operation of the cooling fan 171 flows in A, B, and D directions and then flows out through the cooling fan 171.
When the cooling fan 171 operates, air may flow in C and E directions because of airflow characteristics. Heat generated in the fusing unit 140 is transmitted through C and D directions to the developer unit 120. Thus, temperatures of the developer unit 120 and the photosensitive drum 121 are increased.
An increase in the temperature of the photosensitive drum 121 causes a reduction of a usable period of the photosensitive drum 121. In particular, if a temperature of toner is 55° C. or more, characteristics of toner are changed. Thus, a density of an image quality deteriorates.
Also, due to an increase in a temperature of a waste toner storage (not shown), toner is fused to the waste toner storage, or characteristics thereof are changed, resulting in congelation of the toner. As a result, a load exerted on the cooling apparatus may sharply increase and internal parts of the printer body may be damaged.